supported the United Kingdom's remain campaign during the 2016 EU membership referendum. Chief Whip (2016–2017) Following David Cameron's resignation, Williamson "privately vowed" to stop the front-runner Boris Johnson from becoming Conservative Party leader. He assessed Theresa May to be the likeliest candidate to defeat Johnson, offered his help to her, and was invited to be her parliamentary campaign manager. When May became prime minister, Williamson was appointed Chief Whip. Following the Conservative–DUP agreement after the 2017 general election, Williamson visited Belfast to discuss arrangements with the DUP. Defence Secretary (2017–2019) Williamson was appointed Secretary of State for Defence on 2 November 2017 after the resignation of Sir Michael Fallon the preceding evening. In February 2018, Williamson dined with Lubov Chernukhin, the wife of a former Putin minister, in exchange for a £30,000 donation to the Conservative party. Later that month, Williamson alleged that the leader of the Labour Party, Jeremy Corbyn, in meeting a Czech diplomat (later revealed to be a spy) during the 1980s, had "betray[ed]" his country. In response to the statement, a spokesman for Corbyn stated: "Gavin Williamson should focus on his job and not give credence to entirely false and ridiculous smears". Williamson has supported the Saudi Arabian-led military intervention in Yemen against the Shia Houthis despite concerns from human rights activists and Labour MPs about war crimes allegedly committed by the Saudi military. On 15 March 2018, in the wake of the Salisbury poisoning, Williamson answered a question about Russia's potential response to the UK's punitive measures against Russia by saying that "frankly, Russia should go away, and it should shut up". Major-General Igor Konashenkov, the spokesman of the Russian Defence Ministry, said: "The market wench talk that British defence secretary Gavin Williamson resorted to reflects his extreme intellectual impotency". Williamson's remark was quoted by the president of Ukraine, Petro Poroshenko, who posted a comment on his official Twitter account: "The Kremlin's 'chemical attack' in the UK is nothing but an encroachment on British sovereignty. And our message to Russia is the same as that of British defense secretary Gavin Williamson: 'shut up and go away'." In December 2018, Williamson expressed "grave" and "very deep concerns" about the Chinese telecommunications company Huawei providing technology to upgrade Britain's services to 5G. He accused China of acting "sometimes in a malign way". China's Defence Ministry spokesman Wu Qian criticised Williamson's comments, saying: "The remarks just reinforced the